If everyone has 40 hours a week + overtime and you have a coop that pays competitively for 24 hours a week and no overtime you won't get as much market share, can be outcompeted. It has to be done on a large scale, historically as a matter of policy. This was true for tons of different reductions in the workday and other labor rights improvements in the past.

They can't strategize and adapt very quickly, because of all the cooperating.